1. Field of the Invention
The present invention relates in general to the field of electronic devices and, more particularly, to a portable electronic device that can sense the presence of a user and apply appropriate security measures to the device and/or variable transmission power from the device depending on a distance between the device and the user.
2. Description of the Related Art
The following descriptions and examples are given as background only.
As used herein, an “electronic device” is any device which contains circuitry that allows for communication to and from possibly another electronic device over a transmission medium. The transmission medium can be wired or wireless and the communication signal can be electrical, optical or acoustic. Each electronic device separated by the transmission medium may include a transceiver, which comprises both a transmitter and a receiver. The transceiver can be operably connected to an antenna, which is configured for transmitting and receiving a communication signal at a given power level.
In some cases, it may be desirable to maximize the transmission power supplied to the transmitter, so as to increase the distance and fidelity of the transmitted signal at the receiver end. Unfortunately, radio antennas embedded within portable electronic devices, which are sold both in the United States and Europe, are not allowed to exceed a particular transmission level when the transmitter is placed relatively close to a user. For instance, a mobile phone is one example of a “portable electronic device” that is often held relatively close to a user's ear. If the mobile phone is placed within, for example, two inches of the user's ear, federal regulations will prevent the mobile phone from transmitting at a power level above, for example, 300 mW. This restriction undesirably limits the distance and fidelity of the signals transmitted from the mobile phone (and other portable electronic devices).
One purpose behind forcing some portable electronic devices to transmit at lower transmission power levels is to minimize any electromagnetic energy which could permeate the human body—possibly causing damage thereto. However, the portable electronic device may not be held close to the user at all times. In many instances, there are times during which the portable electronic device may be held at a remote distance away from the user. For example, a tablet computer is another example of a relatively thin, portable electronic device, which often includes a transceiver for sending and receiving communication signals. When held by a user (e.g., on a user's lap or arm), the transmitter included within the tablet computer generally falls within the two inch range during normal usage conditions. However, there may be times during which the tablet will be placed on a table, away from the user's lap or arm, and thus, further than two inches away from the user.
Therefore, it would be desirable to provide a means for selectively changing the transmission power level based on a distance detected between the user and the portable electronic device. This would allow the transmission power to be increased when the portable electronic device is outside of the specified range, and decreased when the portable electronic device is placed relatively close to the user within the specified range. In some cases, it would also be desirable to apply various security measures within the electronic device, depending on the distance detected between the user and the electronic device. For example, as a user approaches the device, heightened security measures can be taken within the device to prevent unauthorized use. Conversely, if a user is outside the range of interest, security measures can be lessened. These benefits are not presently available to conventional portable electronic devices. Thus, it would be desirable to implement one or more of these measures in an improved portable electronic device hereof.